Dear Norberto,

to correct for preferred orientation, Toraya and Marumo seem to apply a 
different correction function than the universally used one proposed by 
Dollase. See Mineralogical Journal, 1980, 10, P 211-221.  They succesfully 
apply it to a monoclinic case study, but you may verify if it is applicable 
also for cubic space groups. Guessing that your are working with Topas, I 
amsure you will not find it difficult to introduce a proper macro in your input.



Kind Regards,

Simona



Save the date: 2014, International Year of Crystallography

*******************************************************
Simona Galli, Dr
Dipartimento di Scienza e Alta Tecnologia
Universit? dell'Insubria
Via Valleggio, 11
22100 Como - Italy

e-mail: simona.ga...@uninsubria.it
tel:    +39-031-2386627
fax:    +39-031-2386630
url:    scienze-como.uninsubria.it/sgalli
*******************************************************

Dear Friends,

I am facing a problem in quantifying magnetite in a complex natural mixture,
using the conventional Rietveld method (in its quantitative analysis approach).
Apparently, the octahedral morphology of (difficult to grind) magnetite crystals
affects itd diffraction pattern.

To my knowledge, as certified in the original paper (JAC 1986, 267-272), the
ubiquitous and highly performing March-Dollase equation, holding for "any"
crystal symmetry, only applies to inequant crystallites (i.e. crystallites with
unequal sides), or, better said, to "effectively rod- or disk-shaped specimens"
(provided that the geometry of the experiments keeps cylindrical symmetry).
Neither octahedral nor cubic (e.g., NaCl) crystals can be considered "inequant".

So, the question is:
Is there any way do get around this problem (without resorting to spherical
hamonics or to grind the specimen in a WC, SiC or BN mill)?

Thank you for your patience.

Norberto






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